Stock material or miscellaneous articles – Hollow or container type article – Nonself-supporting tubular film or bag
Reexamination Certificate
1998-02-12
2001-01-16
Dye, Rena L. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Nonself-supporting tubular film or bag
C428S035500, C428S072000, C428S074000, C428S198000, C428S200000, C428S201000, C428S220000, C428S339000, C383S116000, C383S119000, C156S179000
Reexamination Certificate
active
06174576
ABSTRACT:
FIELD OF THE INVENTION
Closed bags and containers containing sterilized material, such as medium for mycelium production or in vitro cultures, need to be permeable so as to allow the passage or exchange of gases.
THE STATE OF THE ART
Gas-permeable films have the drawback to have low technical properties. The known films can easily be broken, do not have an accurate determined permeability, have a high desiccation rate.
Therefore, it has been proposed to manufacture bags or receptacles made substantially of non permeable film. In order to ensure that said bags or receptacles are suitable for the incubation of mycelium growing medium, it was therefore necessary to provide one end of the bag with a closing means consisting of paper, cotton, wadding or other microporous material. Such bags or receptacles have the following major drawbacks:
high desiccation rate of the growing material in the neighbourhood of the microporous material;
low content of the bag.
Moreover the permeable bags or films have the drawback that the pores are quickly obstructed by mycelium whereby substantially no gases exchange is anymore possible. The growth of mycelium is very quick near the filter, thereby forming a film or barrier against the passage of oxygen. This film or barrier reduces or even avoids the growth of mycelium located under the film or barrier with respect to the permeable closing. It means when using such bags for mycelium growing material, that the incubation is low, not complete and not uniform.
PCT/BE 94/00064 discloses a film provided with a means consisting of fibres having a melting temperature higher than the welding temperature.
In said film, the channels are formed by a plurality of fibres extending substantially parallel to the axis of the channel. During the welding, a movement of the fibres occurs, whereby the permeability of the channels can greatly vary. Furthermore, a movement of the fibres in the channel is possible. A further problem of the film of PCT/BE 94/00064 was its manufacture as, when the tooth of the welding roller exert a welding pressure on the fibres as well as on the films to be welded instead of only on the film to be welded, the fibres are embedded in the welding. Possibly, channels without fibres are formed between the films.
The invention has for subject matter an element such as a film, a packaging bag, a cover means.
BRIEF DESCRIPTION OF THE INVENTION
The invention relates to an element with a determined permeability, said element comprising a first layer and a second layer welded together with interposition of a band of fibres, so as to form a plurality of adjacent welding points or lines, which are separated the one from the other, the fibres of the band having a melting temperature at most 5° C. higher than the melting temperature of at least one of said layers, preferably of said two layers, whereby at the welding points or lines, fibres of the band are molten into the welding points or lines, so that between two adjacent welding points or lines, fibres of the band are not molten and form passage or channel for the exchange of gases but avoiding the passage of solid particles.
The wording “Welding points” means distinct single welding points or a plurality of welding points forming a pattern such as a line.
Preferably, the melting temperature of the fibres is substantially equal to the melting temperature of the layers.
When the first layer and the second layer are welded together by means of welding points, the passage formed between two adjacent welding points has preferably a substantially lenticular cross section, the maximum height of said passage being comprised between 50 &mgr;m and 250.
Advantageously, parts of fibres of the band forming a channel are attached to at least one welding line, preferably to at least two welding lines.
According to an embodiment, the band of fibres is a mat of fibres. In said embodiment, a plurality of channels are formed, each channel having a substantially cylindrical or lenticular shape with a central axis and extending between two adjacent welding lines, some fibres of the mat of a channel which extend in a direction forming an angle of 45 to 90° with respect to the central axis being attached the two adjacent welding lines of said channel.
Preferably, the channels have a substantially circular or lenticular cross section, the height or thickness of which is comprised between 50 &mgr;m and 250 &mgr;m.
According to possible embodiments, the channels have a length comprised between 2 mm and 10 mm, and a width comprised between 50 &mgr;m and 2 mm.
As fibres, it is advantageous to use fibres with a thickness or diameter lower than 10 &mgr;m, preferably lower than 5 &mgr;m and most preferably lower than 2 &mgr;m.
Preferably, the band of fibres has a thickness comprised between 50 and 500 &mgr;m, and most preferably between 50 and 100 &mgr;m. The density of the band before welding is advantageously less than 1000 g/m
2
, preferably less than 500 g/m
2
.
According to another embodiment, the channels have each a central axis, the central axis of said channels intersecting each together substantially in a point. The channels are formed by the micro porosity defined between the fibres of the mat.
According to a further embodiment, the channels extend each between a first end and a second end and have a variable width, said width being substantially minimum at said first end and substantially maximum at said second end.
Preferably, the fibres and the layers are made of the same material. When using the same material, the recycling of the element or film provided with channels is possible and easy to carry out. Material which is particularly suitable is polyethylene, polypropylene, and most preferably a mixture of polypropylene and polyethylene, the said mixture containing advantageously from 70 to 97.5% (preferably 90 to 95%) polypropylene and from 2.5 to 30% (preferably 5 to 10%) polyethylene. By using polypropylene or such mixture, the element according to the invention can be sterilized at temperature of 100-120° C. without problems.
The invention relates also to a cover means for closing a container, at least a part of said cover means consisting of an element with a determined permeability, said element comprising a first layer and a second layer welded together with interposition of a band of fibres, so as to form a plurality of adjacent welding points or preferably welding lines, which are separated the one from the other, the fibres of the band having a melting temperature at most 5° C. higher than the melting temperature of at least one of said layers, preferably of said two layers, whereby at the welding points or lines, fibres of the band are molten into the welding points or lines, so that between two adjacent welding points or lines, fibres of the band are not molten and form a passage or channel for the exchange of gases but avoiding the passage of solid particles.
Advantageously, parts of fibres of the band forming a channel are attached to at least one welding line, preferably to at least two adjacent welding lines.
According to a preferred embodiment, the band of fibres is a band of fibres and in which a plurality of channels are formed, each channel having a cross section with a substantially cylindrical or lenticular shape and with a central axis, said channel extending between two adjacent welding lines, some fibres of the band of a channel which extends in a direction forming an angle of 45 to 90° with respect to the central axis being attached to the two adjacent welding lines of said channel.
The invention relates further to a plastic bag for containing sterilized material, at least a part of said bag consisting of an element comprising a first layer and a second layer welded together with interposition of a band of fibres, so as to form a plurality of adjacent welding points or lines, which are separated the one from the other, the fibres of the band having a melting temperature at most 5° C. higher than the melting temperature of at least one of said layers, preferably of said two layers, wher
Dye Rena L.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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